Back to EveryPatent.com
United States Patent |
6,244,944
|
Elledge
|
June 12, 2001
|
Method and apparatus for supporting and cleaning a polishing pad for
chemical-mechanical planarization of microelectronic substrates
Abstract
A method and apparatus for supporting, cleaning and/or drying a polishing
pad used for planarizing a microelectronic substrate. In one embodiment,
the apparatus can include a cleaning head positioned adjacent a
post-operative portion of the polishing pad to clean and/or dry the rear
surface of the polishing pad. The cleaning head can include a heat source,
a mechanical contact element, and/or orifices that direct fluid and/or gas
toward the rear surface. The apparatus can further include a vessel
through which the rear surface of the polishing pad passes to clean the
rear surface. The apparatus can also include a flow passage in fluid
communication with a region between the polishing pad and a support pad
upon which the polishing pad rests during planarization. Gas moves through
the flow passage toward or away from an interface region between the
polishing pad and the support pad to draw the polishing pad toward or away
from the support pad.
Inventors:
|
Elledge; Jason B. (Boise, ID)
|
Assignee:
|
Micron Technology, Inc. (Boise, ID)
|
Appl. No.:
|
387190 |
Filed:
|
August 31, 1999 |
Current U.S. Class: |
451/296; 451/41; 451/299; 451/307; 451/312; 451/324; 451/443 |
Intern'l Class: |
B24B 021/00 |
Field of Search: |
451/41,296,299,307,312,324,443
|
References Cited
U.S. Patent Documents
6068542 | May., 2000 | Hosokai | 451/37.
|
6086460 | Jul., 2000 | Labunsky et al. | 451/56.
|
6135859 | Oct., 2000 | Tietz | 451/41.
|
Primary Examiner: Gerrity; Stephen F.
Assistant Examiner: McDonald; Shantese
Attorney, Agent or Firm: Dorsey & Whitney LLP
Claims
What is claimed is:
1. An apparatus for removing material from a rear surface of an elongated
polishing pad, the polishing pad having a planarizing surface opposite the
rear surface to planarize a microelectronic substrate, the polishing pad
extending across a platen and having a post-operative portion movable
relative to the platen, the apparatus comprising a cleaning head
positioned proximate to the post-operative portion of the polishing pad
and having at least one cleaning device operable to remove material from
the rear surface of the post-operative portion of the polishing pad.
2. The apparatus of claim 1 wherein the cleaning device includes a contact
element having a cleaning surface positionable to contact the rear surface
of the post-operative portion of the polishing pad.
3. The apparatus of claim 1 wherein the cleaning device includes an orifice
coupleable to a fluid source and facing at least partially toward the rear
surface of the polishing pad to direct fluid toward the rear surface of
the polishing pad and remove material from the rear surface.
4. The apparatus of claim 1 wherein the cleaning device includes a vessel
positioned proximate to the post-operative portion of the polishing pad
and having an opening configured to receive the post-operative portion of
the polishing pad, the vessel having an interior volume in fluid
communication with the opening and configured to contain a quantity of
cleaning liquid sufficient to contact the rear surface of the polishing
pad.
5. The apparatus of claim 1 wherein the polishing pad extends from a supply
roll across the platen to a take-up roll and the cleaning head includes a
body having a first surface toward the platen, a second surface toward the
take-up roll and a slot extending through the body from the first surface
to the second surface to receive the polishing pad, the body further
having a manifold coupled to the fluid source and coupled to a plurality
of orifices positioned within the slot, each orifice being directed toward
the rear surface of the post-operative portion of the polishing pad.
6. The apparatus of claim 1 wherein the polishing pad moves back and forth
across the platen between a supply roll and a take-up roll along a travel
axis, further wherein the cleaning head includes a body having a first
surface toward the platen, a second surface toward the take-up roll, and a
slot aligned with the travel axis and extending through the body from the
first surface to the second surface to receive the polishing pad, the body
further having a manifold coupled to the fluid source and coupled to a
plurality of orifices positioned within the slot, the orifices being
arranged in at least one row oriented transverse to the travel axis, each
orifice being directed toward the rear surface of the post-operative
portion of the polishing pad.
7. The apparatus of claim 1 wherein the polishing pad moves back and forth
across the platen between a supply roll and a take-up roll along a travel
axis, further wherein the cleaning head includes a plurality of orifices
arranged in first and second rows oriented transverse to the travel axis,
orifices of the first row being offset in a direction transverse to the
travel axis from orifices of the second row, the orifices of both the
first and second rows being coupled to a source of heated gas to remove
liquid from the rear surface of the polishing pad by evaporation.
8. The apparatus of claim 1 wherein the polishing pad moves back and forth
across the platen between a supply roll and a take-up roll along a travel
axis and the cleaning head has an orifice coupleable to a fluid source and
facing at least partially toward the rear surface of the polishing pad,
the orifice including a slot elongated along an axis generally transverse
to the travel axis.
9. The apparatus of claim 1 wherein the cleaning head has an orifice facing
at least partially toward the rear surface of the polishing pad and
coupled to a source of high vapor pressure liquid.
10. The apparatus of claim 9 wherein the high vapor pressure liquid is
selected from alcohol and acetone.
11. The apparatus of claim 1 wherein the cleaning head has an orifice
facing at least partially toward the rear surface of the polishing pad and
coupled to a source of gas.
12. The apparatus of claim 11 wherein the gas has a pressure of from
approximately 10 to approximately 100 psi.
13. The apparatus of claim 11 wherein the source of gas includes air.
14. The apparatus of claim 1 wherein the cleaning head has an orifice
facing at least partially toward the rear surface of the polishing pad and
coupleable to a fluid source, further comprising a temperature controller
in fluid communication with the orifice to control a temperature of fluid
passing through the orifice.
15. The apparatus of claim 14 wherein the temperature controller is
configured to control the temperature of fluid passing through the orifice
to be less than approximately 100 degrees Celsius.
16. The apparatus of claim 1 wherein the polishing pad moves back and forth
across the platen between a supply roll and a take-up roll along a travel
axis, further wherein the cleaning head has a contact element with the
cleaning surface positionable to contact the rear surface of the
post-operative portion of the polishing pad, the contact element including
a generally impermeable blade elongated along an axis transverse to the
travel axis and positionable to press against the polishing pad and form
an at least approximately liquid tight seal with the polishing pad to
remove liquid from the polishing pad as the polishing pad moves relative
to the cleaning surface.
17. The apparatus of claim 1 wherein the cleaning head has a contact
element with a cleaning surface positionable to contact the rear surface
of the post-operative portion of the polishing pad, the contact element
including an absorbent brush.
18. The apparatus of claim 17 wherein the absorbent brush is coupled to a
heating element to discharge liquid absorbed by the absorbent brush.
19. The apparatus of claim 1, further comprising a vacuum source in fluid
communication with the polishing pad to draw the polishing pad against the
cleaning surface of the contact element.
20. The apparatus of claim 1 wherein the cleaning head has a plurality of
cleaning surfaces, each being positionable to contact the rear surface of
the polishing pad to remove material from the rear surface.
21. The apparatus of claim 1 wherein the cleaning head has a first orifice
in fluid communication with a source of pressurized gas and a second
orifice in fluid communication with a source of cleaning liquid, the first
and second orifices being directed toward the rear surface of the
polishing pad.
22. The apparatus of claim 1 wherein the cleaning head has a heat source
positioned proximate to the rear surface of the post-operative portion of
the polishing pad to direct heat toward the rear surface of the polishing
pad and dry the rear surface.
Description
TECHNICAL FIELD
The present invention is directed toward methods and apparatuses for
supporting, cleaning and/or drying a polishing pad used for mechanical
and/or chemical-mechanical planarization.
BACKGROUND OF THE INVENTION
Mechanical and chemical-mechanical planarizing processes (collectively
"CMP") are used in the manufacturing process of microelectronic devices to
form a flat surface on semiconductor wafers, field emission displays, and
many other microelectronic-device substrates and substrate assemblies.
FIG. 1 is a partially schematic, isometric view of a conventional
web-format planarizing machine 10 that has a platen 20. A sub-pad 11 is
attached to the platen 20 to provide a flat, solid workstation for
supporting a portion of a web-format polishing pad 16 in a planarizing
zone "A" during planarization. The polishing pad 16 has a rear surface 19
that engages the sub-pad 11 and a planarizing surface 18 facing opposite
the rear surface 19 to planarize a substrate 12.
The planarizing machine 10 also has a pad-advancing mechanism, including a
plurality of rollers, to guide, position and hold the polishing pad 16
over the sub-pad 11. The pad-advancing mechanism generally includes a
supply roller 24, first and second idler rollers 21a and 21b, first and
second guide rollers 22a and 22b, and a take-up roller 23. As explained
below, a motor (not shown) drives the take-up roller 23 and the supply
roller 24 to advance and retract the polishing pad 16 over the sub-pad 11
along a travel path T--T. The first idler roller 21a and the first guide
roller 22a press an operative portion of the polishing pad 16 against the
sub-pad 11 to hold the polishing pad 16 stationary during operation.
The planarizing machine 10 further includes a carrier assembly 30 to
translate the substrate 12 over the polishing pad 16. In one embodiment,
the carrier assembly 30 has a head 31 to pick up, hold and release the
substrate 12 at appropriate stages of the planarizing process. The carrier
assembly 30 also has a support gantry 32 and a drive assembly 33 that can
move along the gantry 32. The drive assembly 33 has an actuator 34, a
drive shaft 35 coupled to the actuator 34, and an arm 36 projecting from
the drive shaft 35. The arm 36 carries the head 31 via a terminal shaft
37. The actuator 34 orbits the head 31 about an axis B--B (as indicated by
arrow R.sub.1) and can rotate the head 31 about an axis C--C (as indicated
by arrow R.sub.2) to move the substrate 12 over the polishing pad 16 while
a planarizing fluid 17 flows from a plurality of nozzles 38 in the head
31. The planarizing fluid 17 may be a conventional CMP slurry with
abrasive particles and chemicals that etch and/or oxidize the surface of
the substrate 12, or the planarizing fluid 17 may be a non-abrasive
planarizing solution without abrasive particles. In most CMP applications,
conventional CMP slurries are used on conventional polishing pads, and
planarizing solutions without abrasive particles are used on
fixed-abrasive polishing pads.
In the operation of the planarizing machine 10, the carrier assembly 30
presses the substrate 12 against the planarizing surface 18 of the
polishing pad 16 as the carrier head 31 moves the substrate 12 over the
planarizing surface 18. The polishing pad 16 moves across the sub-pad 11
along the pad travel path T--T either during or between planarizing cycles
to change the particular portion of the polishing pad 16 in the
planarizing zone A. For example, the supply and take-up rollers 24, 23 can
drive the polishing pad 16 between planarizing cycles such that a point P
moves incrementally across the sub-pad 11 to a number of intermediate
locations I.sub.1, I.sub.2, etc. Alternatively, the rollers 24, 23 may
drive the polishing pad 16 between planarizing cycles such that the point
P moves all the way across the sub-pad 11 toward the take-up roller 23 to
completely remove a used or post-operative portion of the polishing pad 16
from the planarizing zone A. The rollers 24, 23 may also continuously
drive the polishing pad 16 at a slow rate during a planarizing cycle such
that the point P moves continuously across the sub-pad 11 during
planarization.
The planarizing machine 10 can also include a planarizing surface cleaner
40 (shown schematically in FIG. 1) positioned between the platen 20 and
the take-up roller 23 to clean the post-operative portion of the polishing
pad 16. The planarizing surface cleaner 40 can include a brush 41 having
bristles that contact the planarizing surface 18 of the polishing pad 16
and a liquid dispenser 42 positioned proximate to the brush 41 to dispense
a cleaning liquid on the planarizing surface 18. Accordingly, the
planarizing surface cleaner 40 can clean the post-operative portion of the
polishing pad 16 as it moves off the platen 20 along the travel path T--T.
Once the post-operative portion of the polishing pad 16 has been cleaned,
it can be translated back onto the platen 20 along the travel path T--T
and into the planarizing zone A for another planarizing cycle.
One drawback with the apparatus 10 shown in FIG. 1 is that the rear surface
19 of the polishing pad 16 can become contaminated with debris (such as
liquid and/or particulate matter) during the planarizing process and/or
the cleaning process. The debris can become trapped between the polishing
pad 16 and the sub-pad 11, causing a local bump or other non-uniformity to
form in the planarizing surface 18. The non-uniformity in the planarizing
surface 18 can create a non-uniformity in the substrate 12 and/or can
cause the polishing pad 16 to wear in a non-uniform manner.
A further drawback is that liquid on the rear surface 19 of the polishing
pad 16 can form an adhesive bond between the polishing pad 16 and the
sub-pad 11. The adhesive bond can inhibit relative movement between the
polishing pad 16 and the sub-pad 11 when the polishing pad 16 moves along
the travel path T--T. In one conventional method, the idler rollers 21a,
21b and/or the guide roller 22a move the polishing pad 16 normal to the
upper surface of the sub-pad 11 to break the adhesive bond. However, the
action of the rollers against the polishing pad 16 may not be effective to
separate the polishing pad 16 from the sub-pad 11. Furthermore, if the
polishing pad 16 is dragged over the sub-pad 11, the frictional contact
between the two can abrade particulate matter from the polishing pad 16
and/or the sub-pad 11, which can cause a bump or other non-uniformity to
form in the planarizing surface 18, as discussed above.
SUMMARY OF THE INVENTION
The present invention is directed toward methods and apparatuses for
supporting, cleaning and/or drying a polishing pad used for mechanical
and/or chemical planarization of microelectronic substrates and substrate
assemblies. In one aspect of the invention, a cleaning head is positioned
proximate to a post-operative portion of the polishing pad to remove
material from a rear surface of the polishing pad that faces opposite a
planarizing surface of the polishing pad. The cleaning head can have a
cleaning device operable to remove liquid and/or particulate material from
the rear surface. For example, the cleaning device can include a contact
element such as an absorbent brush or an impermeable blade positionable to
contact the rear surface of the post-operative portion of the polishing
pad, an orifice facing toward the rear surface of the polishing pad to
provide gas or liquid to the rear surface, and/or a heat source to dry the
rear surface of the polishing pad. Alternatively, the cleaning head can
include a vessel proximate to the post-operative portion of the polishing
pad. The vessel can have an opening configured to receive the
post-operative portion and an interior volume in fluid communication with
the opening and configured to contain a quantity of cleaning liquid
sufficient to contact the rear surface of the polishing pad. The vessel
can further include an ultrasonic transducer to transmit ultrasonic energy
to the cleaning liquid.
In an embodiment in accordance with still a further aspect of the
invention, the polishing pad can be supported on a support surface, such
as a surface of a support pad. Gas or liquid is directed toward or away
from an interface region between the support surface and the rear surface
of the polishing pad to separate the polishing pad from the support
surface, or draw the polishing pad toward the support surface.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a partially schematic, front isometric view of a web-format
planarizing machine in accordance with the prior art.
FIG. 2 is a partially schematic, partially broken, front isometric view of
a planarizing machine having a cleaning head in accordance with an
embodiment of the invention.
FIG. 3 is a partially schematic, partially broken, front isometric view of
a planarizing machine having a cleaning head and a liquid vessel in
accordance with another embodiment of the invention.
FIG. 4 is a partially schematic, top isometric view of a portion of a
planarizing machine having a platen coupled to a gas source and a vacuum
source in accordance with another embodiment of the invention.
FIG. 5 is a partially schematic, top isometric view of a portion of a
planarizing machine having a platen with orifices coupled to a gas source
and a vacuum source in accordance with another embodiment of the
invention.
FIG. 6 is a partially schematic, top isometric view of a portion of a
planarizing machine having a platen and a support pad with orifices
coupled to a gas source and a vacuum source in accordance with still
another embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is directed toward methods and apparatuses for
supporting, cleaning and/or drying planarizing media used to planarize
microelectronic substrates and/or substrate assemblies. Many specific
details of certain embodiments of the invention are set forth in the
following description and in FIGS. 2-6 to provide a thorough understanding
of such embodiments. One skilled in the art, however, will understand that
the present invention may have additional embodiments, or that the
invention may be practiced without several of the details described in the
following description.
FIG. 2 is a partially schematic, side isometric view of planarizing machine
110 having a polishing pad 116 that passes through a cleaning head 150 and
adjacent a planarizing surface cleaner 140 in accordance with an
embodiment of the invention. The polishing pad 116 extends from a supply
roller 124 across a platen 120 and a support pad 111 to a take-up roller
123, while being controlled and guided by an idler roller 121 and two
guide rollers 122a, 122b generally as was discussed above. The polishing
pad 116 has a planarizing surface 118 facing toward a microelectronic
substrate or substrate assembly 112 and a rear surface 119 facing opposite
the planarizing surface 118. A carrier assembly 130 positioned adjacent
the polishing pad 116 can include a head 131 having an engaging surface
139 that presses the substrate 112 against the polishing pad 116 during
operation. A drive assembly 133 supported by a gantry 132 and including an
actuator 134, a drive shaft 135, an arm 136 and a terminal shaft 137 moves
the head 131 relative to the polishing pad 116 to remove material from the
substrate 112. The polishing pad 116 advances from the supply roller 124
to the take-up roller 123 either between or during planarizing cycles, in
a manner generally similar to that discussed above.
The polishing pad 116 includes a pre-operative portion 113 between the
supply roller 124 and the platen 120 and a post-operative portion 114
between the platen 120 and the take-up roller 123. As the polishing pad
116 advances along the travel path T--T toward the take-up roller 123, the
pre-operative portion 113 moves onto the platen 120 to planarize the
substrate 112 and the post-operative portion 114 moves off the platen 120
for cleaning. Accordingly, the planarizing surface cleaner 140 and the
cleaning head 150 are positioned proximate to the post-operative portion
114 between the platen 120 and the take-up roller 123.
In one embodiment, the planarizing surface cleaner 140 includes a brush 141
having bristles that engage the planarizing surface 118 of the polishing
pad 116 to remove particulates and other contaminants from the planarizing
surface 118, or the planarizing surface cleaner 140 can include other
cleaning elements. The planarizing surface cleaner 140 also includes a
liquid dispenser 142 coupled with a conduit 143 to a source of cleaning
liquid (not shown). The liquid dispenser 142 can have orifices facing
toward the planarizing surface 118 to dispense the cleaning liquid onto
the planarizing surface 118. The mechanical action provided by the brush
141 in combination with the chemical and/or mechanical action provided by
the cleaning liquid clean the planarizing surface 118 of the
post-operative portion 114 before the post-operative portion 114 returns
to the platen 120 along the travel path T--T for the next planarizing
cycle.
The cleaning head 150 is positioned between the planarizing surface cleaner
140 and the platen 120 to clean and/or dry the rear surface 119 of the
polishing pad 116 before the post-operative portion 114 of the polishing
pad 116 returns to the platen 120. The cleaning head 150 can include a
body 151 with an upper surface 153, a lower surface 154 and a slot 152
extending through the body 151 from the upper surface 153 to the lower
surface 154, or the cleaning head 150 can have other configurations to
receive the polishing pad 116. In one embodiment, the cleaning head 150
includes a liquid manifold 170 positioned within the slot 152 and coupled
to a liquid source 174 with a liquid conduit or passage 171. The liquid
manifold 170 has one or more liquid orifices 172 pointing toward the rear
surface 119 of the polishing pad 116 to direct the cleaning liquid toward
the rear surface 119. In one aspect of this embodiment, the cleaning
liquid has a high vapor pressure so that it evaporates quickly, leaving
the rear surface 119 dry before the post-operative portion 114 of the
polishing pad 116 returns to the platen 120. For example, the cleaning
liquid can include acetone, alcohol, or other liquids having a relatively
high vapor pressure. Alternatively, the vapor pressure of the cleaning
liquid may not be particularly high and the rate at which the polishing
pad 116 moves back onto the platen 120 can be reduced (or the polishing
pad 116 can remain in a fixed position) while the cleaning liquid
evaporates from the rear surface 119.
In one embodiment, the cleaning head 150 includes one or more gas manifolds
160 to hasten the drying of the rear surface 119 and/or to clean the rear
surface 119. In one aspect of this embodiment, the cleaning head 150 has
three gas manifolds 160 (shown as an upper manifold 160a, an intermediate
manifold 160b and a lower manifold 160c) and in other embodiments, the
cleaning head has more or fewer manifolds 160, as will be discussed in
greater detail below. Each gas manifold 160 is coupled via a gas conduit
or passage 161 to a gas source 164 to provide gas to the manifolds 160.
The gas source 164 can include any suitable gas, such as air, or an inert
gas, compressed to an elevated pressure of, for example, between about 10
psi and about 100 psi, or another suitable pressure.
Each gas manifold 160 is also in fluid communication with one or more
orifices 162 (shown in FIG. 2 as circular upper orifices 162a, circular
intermediate orifices 162b and an elongated lower orifice 162c) to direct
the gas toward the rear surface 119 of the polishing pad 116. The upper
and intermediate orifices 162a, 162b can include discrete circular
openings arranged in rows transverse to the travel direction T--T of the
polishing pad 116 or the orifices 162a, 162b can have other shapes or
configurations. In one embodiment, the upper orifices 162a are offset or
staggered transversely relative to the intermediate orifices 162b to
uniformly distribute the gas over the width of the rear surface 119. In
one aspect of this embodiment, the orifices 162a, 162b are directed at
least partially downward so that the gas emitted from the orifices 162a,
162b forces liquid and/or contaminants downwardly away from the rear
surface 119 as the post-operative portion 114 moves upwardly back onto the
platen 120. Alternatively, the orifices 162a, 162b can have other
orientations.
In yet a further aspect of this embodiment, the lower orifice 162c includes
a slot elongated in a direction generally transverse to the travel path
T--T and directed at least slightly downward, as was discussed above. The
lower gas manifold 160c is coupled to a temperature controller 163 to
control the temperature of the gas directed toward the rear surface 119 of
the polishing pad 116. For example, in one embodiment, the temperature
controller 163 can control the temperature of the gas be up to and
including approximately 100.degree. C. In other embodiments, the
temperature controller 163 can elevate the temperature of the gas to other
values that do not adversely affect the polishing pad 116.
In still further embodiments, other combinations and arrangements of the
elements discussed above with reference to FIG. 2 can clean and/or dry the
rear surface 119 of the polishing pad 116. For example, the cleaning head
150 can include a single row of orifices 162 or can include more than two
rows of orifices 162, any of which can be coupled to the temperature
controller 163. Alternatively, the cleaning head 150 can include the
elongated orifice 162c in lieu of, rather than in addition to, the
circular orifices 162a, 162b. In another embodiment, the gas manifold(s)
160 can be eliminated, for example, when the liquid manifold 170 provides
liquid sufficient to adequately clean the rear surface 119 of the
polishing pad 116 and the liquid evaporates before the post-operative
portion 114 moves back onto the platen 120. Conversely, when the gas
provided by the gas manifold(s) 160 is sufficient to both clean and dry
the rear surface 119, the liquid manifold 170 can be eliminated.
One feature of an embodiment of the apparatus 110 discussed above with
reference to FIG. 2 is that the cleaning head 150 removes liquid and/or
solid contaminants from the rear surface 119 of the polishing pad 116
before the post-operative portion 114 of the polishing pad 116 returns to
the platen 120. An advantage of this arrangement is that the planarizing
surface 118 of the polishing pad 116 is less likely to have
non-uniformities resulting from contaminants trapped between the polishing
pad 116 and the support pad 111. A further advantage of this arrangement
is that the likelihood for the polishing pad 116 to adhere to the support
pad 111 (due to the presence of liquid between the two) can be reduced,
increasing the ease with which the polishing pad 116 is moved across the
platen 120. This is unlike some conventional planarizing devices which not
only allow liquid and/or solid debris to accumulate on the rear surface
119 of the polishing pad 116 but also fail to remove such contaminants
before the polishing pad 116 returns to the platen 120.
FIG. 3 is a partially schematic, partially broken side isometric view of an
apparatus 210 having a cleaning head 250 in accordance with another
embodiment of the invention. The cleaning head 250 includes a body 251
having a slot 252 through which the polishing pad 116 passes. In one
embodiment, two contact elements 280 (shown as a wiper 280a and an
absorbent brush 280b) are positioned within the slot to remove
contaminants from the rear surface 119 of the polishing pad 116. The
contact elements 280 can be coupled to an actuator 286 that moves the
contact elements 280 into and out of engagement with the rear surface 119,
or the contact elements 280 can remain pressed against the rear surface
119. In other embodiments, the cleaning head 250 can include more or fewer
contact elements 280 and/or contact elements 280 in combination with fluid
manifolds and/or gas manifolds, similar to those discussed above with
reference to FIG. 2.
In one embodiment, the wiper 280a includes an impermeable, resilient and
flexible material, such as rubber or another elastomer having one or more
edges 281 (two are shown in FIG. 3) or other cleaning surfaces that
contact the rear surface 119 of the polishing pad 116. In a further aspect
of this embodiment, the wiper 280a has vacuum orifices 283 facing toward
the rear surface 119 and coupled with a vacuum conduit 282 to a vacuum
source (not shown). When a vacuum is applied to the vacuum orifices 283
via the vacuum conduit 282, the polishing pad 116 is drawn against the
wiper 280a so that the rear surface 119 contacts the edges 281, forming an
at least partially liquid-tight seal. Alternatively, the vacuum orifices
283 can be housed in a separate unit (not shown) adjacent to the wiper
280a. In either case, the edges 281 of the wiper 280a deflect liquid
and/or solid contaminants from the rear surface 119 as the polishing pad
116 moves upwardly onto the platen 120.
The cleaning head 250 can include the absorbent brush 280b in addition to,
or in lieu of the wiper 280a. In one embodiment, the absorbent brush 280b
has a cleaning surface that includes any resilient, compliant and
absorbent material (such as polyvinyl alcohol) to absorb liquid from the
polishing pad 116 without abrading the polishing pad 116. In one aspect of
this embodiment, the absorbent brush 280b has a heating element 285
coupled to an electrical source (not shown) with electrical leads 284 to
remove moisture from the absorbent brush 280b after the absorbent brush
280b has absorbed moisture from the rear surface 119 of the polishing pad
116. In other embodiments, other devices (for example, rollers or forced
heated air) discharge moisture from the absorbent brush 280b. In still
another embodiment, the absorbent brush 280b (or another contact element
280, such as the wiper 280a) is heated while it is pressed against the
polishing pad 116.
In yet another embodiment, the cleaning head 250 includes the heating
element 285 alone instead of the contact elements 280. For example, the
heating element 285 can include an electric coil heater or an infrared
heater that removes moisture from the rear surface 119 of the polishing
pad without contacting the polishing pad 116. In one embodiment, the
heating element 285 operates in conjunction with devices that clean the
rear surface 119 (such as the gas manifolds 160 and liquid manifolds 170
discussed above with reference to FIG. 2) or alternatively the heating
element 285 operates independently of the cleaning devices, for example,
when it is desired only to dry the rear surface 119, rather than both
clean and dry the rear surface 119.
In one embodiment, the cleaning head 250 includes a cleaning vessel 290 in
addition to or in lieu of the planarizing surface cleaner 140 discussed
above with reference to FIG. 2. The cleaning vessel 290 has an internal
volume 292 with an opening 291 configured to receive the polishing pad
116. The internal volume 292 contains a cleaning liquid 293, such as a
solvent, to remove contaminants from the polishing pad 116. In one aspect
of this embodiment, the polishing pad 116 passes around a guide roller 222
submerged in the cleaning liquid 293 to immerse both the planarizing
surface 119 and the rear surface 118 of the polishing pad 116.
Alternatively, the cleaning vessel 290 can include other devices that
immerse the planarizing surface 118 and/or the rear surface 119. The
vessel 290 can also include ultrasonic transducers 294 adjacent to the
internal volume 292 to direct ultrasonic energy into the cleaning liquid
293, increasing the efficacy of the cleaning liquid 293.
In one embodiment, the cleaning liquid 293 includes a relatively high vapor
pressure liquid, such as acetone or alcohol, that evaporates from the
polishing pad 116 before the post-operative portion 114 of the polishing
pad 116 returns to the platen 120. Accordingly, the body 251 of cleaning
head 250 can be eliminated. Alternatively, the vessel 290 can include
other liquids 293 (such as water) that do not evaporate as readily as
acetone or alcohol, in which case the contact elements 280, the heating
element 285, and/or the gas manifolds 160 discussed above can remove
excess liquid from the rear surface 119 of the polishing pad 116 before
the polishing pad 116 returns to the platen 120.
One feature of an embodiment of the apparatus 210 shown in FIG. 3 is that
the cleaning vessel 290 cleans the polishing pad 116 without direct
mechanical contact other than that resulting from the roller 222.
Accordingly, the likelihood for abrading the polishing pad 116 during
cleaning is reduced when compared with some conventional devices. The
likelihood for abrasion can be further reduced by drying the polishing pad
116 with the heater 285 or with gas from the gas manifold(s) 160 (FIG. 2)
or by allowing the cleaning liquid 293 to evaporate before the polishing
pad 116 returns to the platen 120.
FIG. 4 is a partially schematic, top isometric view of a portion of a
planarizing apparatus 310 having a platen 320 that supports the polishing
pad 116 (shown in phantom lines) in accordance with another embodiment of
the invention. In one aspect of this embodiment, the apparatus 310
includes a support pad 311 positioned between the rear surface 119 of the
polishing pad 116 and an upwardly facing support surface 322 of the platen
320. The platen 320 can further include a channel 325 that extends around
the perimeter of the support pad 311 and has an upwardly facing opening
adjacent to the rear surface 119 of the polishing pad 116. The channel 325
is coupled with a conduit 326 to a pressurized gas source 327 and a vacuum
source 328. A valve 323 in the conduit 326 can be manually or
automatically controlled to connect either the gas source 327 or the
vacuum source 328 with the channel 325.
In operation, the valve 323 is adjusted to connect the vacuum source 328
with the channel 325 during planarization of the substrate 112 (FIGS.
2-3). Accordingly, the polishing pad 116 is drawn tightly against the
support pad 311 to prevent unwanted movement of the polishing pad 116
which can result in non-uniformities in the substrate 112. When the
polishing pad 116 is to be moved relative to the platen 320 (for example,
to be cleaned according to one or more of the methods discussed above with
reference to FIGS. 2-3), the valve 323 is adjusted to couple the gas
source 327 to the channel 325. The gas source 327 pumps a gas (such as
air) through the channel 325 to impinge on the rear surface 119 of the
polishing pad 116 and flow to an interface region between the polishing
pad 116 and the support pad 311. The pressurized gas separates the
polishing pad 116 slightly from the support pad 311, allowing the
polishing pad 116 to be more easily moved relative to the support pad 311
and the platen 320. Furthermore, the compressed gas can remove
contaminants, such as liquid or solid debris, from the rear surface 119 of
the polishing pad 116. Accordingly, an advantage of an embodiment of the
apparatus 310 shown in FIG. 4 is that it can clean and dry the rear
surface 119 and/or separate the rear surface 119 from the support pad 311
for moving the polishing pad 116 relative to the platen 320.
FIG. 5 is a partially schematic, partially broken top isometric view of a
portion of a planarizing apparatus 410 having a platen 420 and a support
pad 411 that support the polishing pad 116 in accordance with another
embodiment of the invention. The platen 420 includes a plurality of
orifices 429 arranged around the perimeter of the support pad 411 and
coupled to a plenum 421 positioned within the platen 420. The plenum 421
is coupled via the conduit 326 to the gas source 327 and the vacuum source
328 in a manner generally similar to that discussed above with reference
to FIG. 4. Accordingly, the plenum 421 can be selectively coupled to the
gas source 327 and the vacuum source 328 to either expel or draw in air in
a manner generally similar to that discussed above with reference to FIG.
4.
FIG. 6 is a partially schematic, partially broken top isometric view of a
portion of an apparatus 510 having a platen 520 and a support pad 511 that
support the polishing pad 116 in accordance with yet another embodiment of
the invention. The platen 520 includes a plenum 521 coupled to the gas
source 327 and the vacuum source 328 in a manner similar to that discussed
above. The apparatus 510 further includes a plurality of orifices 529,
including pad orifices 529a extending through the support pad 511 and
aligned with a corresponding plurality of platen orifices 529b extending
through a portion of the platen 520 to be in fluid communication with the
manifold 521. The orifices 529 can be uniformly spaced over the support
pad 511, or alternatively, the orifices can be arranged in other patterns.
In a further aspect of this embodiment, the orifices 529 can point toward
the edges of the support pad 511 and the polishing pad 116 to direct
contaminants outwardly away from the interface region between the support
pad 511 and the polishing pad 116. The orifices 529 are selectively
coupled to either the gas source 327 or the vacuum source 328 to operate
in a manner similar to that discussed above with reference to FIG. 4.
From the foregoing it will be appreciated that, although specific
embodiments of the invention have been described herein for purposes of
illustration, various modifications may be made without deviating from the
spirit and scope of the invention. Accordingly, the invention is not
limited except as by the appended claims.
Top